Glossary
Sleep Cycle
The repeating pattern of NREM sleep and REM sleep that occurs throughout the night. A full sleep cycle typically lasts 90–110 minutes and repeats several times, guiding the body through different stages of brain activity and physical restoration.
REM Sleep
A state of sleep that recurs cyclically with non-REM sleep several times during a normal period of sleep, characterized especially by greatly depressed muscle tone, dreaming with vivid imagery, rapid eye movements, and increased neuronal activity in certain brain regions (such as the pons). It typically comprises up to 25% of time spent in sleep.
NREM Sleep
A state of sleep that occurs regularly during a normal period of sleep with intervening periods of REM sleep and is characterized by delta wave brain activity, minimal dreaming, and a reduced level of autonomic physiological activity.
Blue Light Filter
A screen setting or external tool that reduces the amount of blue-wavelength light emitted by a device. Blue light filters help reduce eye strain and minimize interference with the body's natural melatonin production, which can impact sleep.
Circadian Rhythm
The internal 24-hour biological clock that regulates sleep, wakefulness, hormone release, body temperature, and other daily physiological processes based on patterns of light and darkness.
Sleep Debt
The cumulative effect of not getting enough sleep over time. Sleep debt builds up when a person consistently sleeps fewer hours than their body needs, leading to fatigue, impaired cognitive performance, and other negative health effects.